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Add iszero.

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TS 18661-1 adds an iszero classification macro to <math.h>.  This
patch implements it for glibc.  There are no new underlying functions
in libm because the implementation uses fpclassify when sNaN support
is required and a direct comparison otherwise; any optimizations for
this macro should be done through adding __builtin_iszero in GCC and
using it in the header for suitable GCC versions, not through adding
other optimized inline or out-of-line versions to glibc.

Tested for x86_64 and x86.

	* math/math.h [__GLIBC_USE (IEC_60559_BFP_EXT)] (iszero): New
	macro.
	* math/libm-test.inc (iszero_test_data): New array.
	(iszero_test): New function.
	(main): Call iszero_test.
	* manual/arith.texi (Floating Point Classes): Document iszero.
	* manual/libm-err-tab.pl: Update comment on interfaces without
	ulps tabulated.
This commit is contained in:
Joseph Myers
2016-09-23 21:54:21 +00:00
parent 4775578486
commit bb8081f57f
6 changed files with 55 additions and 3 deletions
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7
math/math.h
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@ -331,6 +331,13 @@ enum
/* Return nonzero value if X is subnormal. */
# define issubnormal(x) (fpclassify (x) == FP_SUBNORMAL)
/* Return nonzero value if X is zero. */
# ifdef __SUPPORT_SNAN__
# define iszero(x) (fpclassify (x) == FP_ZERO)
# else
# define iszero(x) ((x) == 0)
# endif
#endif /* Use IEC_60559_BFP_EXT. */
#ifdef __USE_MISC